The means for preparing the sheets, films, and objects from various viscosities and forms of polymers has been known to require the use of pellets of the polymers. The resin of the melted polymer is passed through an extruder, and the barrel of the extruder may have vacuum venting in order to remove the humidity created during the extrusion process. A melt pump is used in order to produce an even melt throughput as it is pushed towards the extrusion die. Next, the molten resin is formed into a sheet or film by passing through an extrusion die. In the case of the rotary die, the objects are manufactured directly onto the rotary die and do not pass through the sheet phase. The sheet or film is then polished in a roll stack or passed through a calendar stack where the product is sized to the appropriate thickness. The sheet can then be surface treated with silicone on one or both sides. In the case of strapping material, the sheet is typically slit into strapping material. Finally, the sheet or film is then wound into a roll or slit and cut into finished sheets. Alternatively, film could be formed by the above process or by pumping through an annular die and expanding the molton polymer cylinder with air. This is referred to as the “bubble process.” Typically, only film is produced with the bubble process. Generally, sheet is referred to as material having a thickness greater than 5-7 mils and film as material having a thickness of less than 5-7 mils. Oftentimes, material having a thickness of 5-7 mils may be referred to as either.
These various processes affect the performance of the polymer pellets when they are converted into a sheet form or injected onto a rotary die. In general, the physical properties of the polymers, such as its hygroscopicity in pellet form, negatively impact the polymers optical properties of the finished product if not adequately conditioned. When extruded, side reactions lead to the degradation of the polyester chain negatively impacting the properties. Furthermore, it has been a common practice to compensate for some of polymer pellets negative performances as pertaining to the hydroscopicity and degradation the viscosity levels during the extrusion process.
Two primary polymer processes for the manufacture of polymer include solution or slurry polymerization processes. Slurry and solution polymerization processes are usually free radical processes that are used to manufacture a great many polymers. The distinct advantage of these polymerization processes is the reaction temperature is controlled and maintained at a lower temperature and most of these reactions are also run as lower pressures. One disadvantage is that the solvent of diluent has to be removed prior to the processing. The two polymerization processes are different from one another in that the solution polymerization has the polymer dissolved in the solvent while the slurry process has the polymer suspended in the diluents.